The Daily Mailreported on 5 May this year that: "Half an hour after seeing the film Alice in Wonderland in 3D, Josh James blacked out on his way home and rolled his car. Could 3D have been to blame?"

James certainly thinks so, and many newspapers seem to share his opinion. In recent months we've been bombarded with alarming stories about 3D, from tales of 3D monitors and movies damaging our eyesight to The Sun's claims that some Nintendo 3DS users "even reported seeing web pages in 3D after switching from the console to a PC."

With manufacturers' own safety warnings suggesting pregnant women, children and drinkers should avoid the technology, it's no wonder that some people are concerned. But is there any substance behind the scares, or are people seeing problems that aren't really there?

Screen-related scares like these are nothing new, and sometimes there's real substance to people's concerns. For example, the advice that you shouldn't sit too close to the TV dates back to May 1967, when General Electric admitted that poor shielding meant some of its TV sets emitted dangerously high levels of X-ray radiation.

As Time magazine reported, "Because the radiation was directed downwards, [Public Health Service] officials noted that most viewers would probably not be harmed. But they worried about children sitting on the floor near TV sets placed on tables or shelves. X-rays shooting through vents in the bottom of such sets could produce serious eye damage within an hour."

The problem was fixed 44 years ago, but we're still warning children about sitting too close to screens today - although our focus has shifted to concerns about our children developing 'square eyes' from televisions, computer monitors and games consoles. Sitting too close to any screen for too long can certainly cause eyestrain, but it doesn't do any permanent damage. It won't make a child myopic (short-sighted), but a child who is developing myopia may well start sitting closer to the screen so he or she can see it better.

That leads to understandable confusion between causation and correlation: sitting too close was a symptom of the problem, not the cause of it. Could the same confusion be happening with 3D?

What the papers say

According to The Sun, the 3D effect in Nintendo's 3DS has made lots of gamers ill. "Fans besieged gadget websites and Twitter to complain of dizziness, headaches and sickness after playing the hand-held device for just a few minutes," it reported.

According to the Daily Mail, "Studies show that in up to 20 per cent of viewers, [3D] could even induce physical sickness," while Fox News claimed that "From Hollywood studios to Japanese TV makers, powerful business interests are betting 3D will be the future of entertainment, despite a major drawback: it makes millions of people uncomfortable or sick."

Fox News claims that these problems affect one in four viewers; the Daily Mail, one in five; The Sun, "thousands" of "furious gamers". Is any of this actually true?

The short answer is no. The Sun's claim that thousands of goggle-eyed 3DS owners returned their handheld consoles was quickly debunked by Nintendo and our sister magazine T3, which discovered that GAME had received just five complaints, and that Nintendo's return rates were actually lower than with previous launches.

Fox News eventually admitted that its one in four figure came from an "unscientific, online survey" that didn't find 3D made one in four people sick; it found that one in four people who filled out the survey had felt "uncomfortable or sick". That's a big difference.

The Daily Mail story was based on a single study of just 39 people, none of whom were actually sick. It's clear that some exaggeration is happening, but that doesn't mean 3D doesn't cause problems. It can, and it does.

A dangerous dimension?

There are three key concerns about 3D. The first is that it could make you ill, causing symptoms like severe headaches, fatigue and nausea. The second is that it could cause disorientation, leading to events like Josh James' car crash. The third concern is that it could damage children's vision.

Of the three, there's no doubt that the first and second concerns are valid; we can get the same symptoms from simply looking at 2D displays, reading books and staring through car windscreens at the road ahead. Focusing on a single point for too long fatigues the eye muscles and causes eyestrain. Its symptoms can include headaches, dizziness, carsickness, light-headedness, nausea, blurred or double vision and concentration problems.

The disorientation Josh James described sounds like a particularly severe case of such strain, but while it was unpleasant and dangerous for him, such symptoms are very rare.

The main factors in eyestrain are the length of exposure and the distance from the screen, but another factor can be the refresh rate of the screen you're looking at. Some people are sensitive to low refresh rates in 2D as well as 3D, and if they're wearing a set of 120Hz active 3D glasses then they're experiencing 60 flashes per second per eye as the glasses' lenses darken and brighten. Faster glasses with a higher refresh rate can help to reduce the effect.

Another factor could be the nature of 3D itself, as Larry Benjamin, Chair of the Education Committee for the Royal College of Ophthalmologists, explains.

"The main principle of 3D imaging is to send one view of a picture to your left eye and a different view of the same scene to the right, which your visual cortex will then put together as a perception of an object with depth," he says. It's a trick, but it doesn't work on everyone.

"Approximately 2-3 per cent of the population can't see 3D because of early onset squint, or an eye problem that develops later in life - and you need good vision in both eyes to be able to see 3D," Benjamin says. "This is because the vision in each eye is slightly different. You can test this by looking at the same object with one eye covered and then looking at it with the other eye covered - the image shifts very slightly. The theory is that this helps us judge depth and distance better."

The study found that for people with good binocular vision (GBS), 3D didn't cause any problems at all. However, people with moderate binocular vision (MBS) "are more susceptible to visual complaints associated with stereoscopic displays."

A later study by the same authors, An Exploration of the Initial Effects of Stereoscopic Displays on Optometric Parameters, concludes: "When healthy adult subjects with normal binocular vision viewed text images at 3-metres in extreme 3D display settings for a short period of time there were no clinically significant mean changes in optometric test variables compared with 2D viewing."

Of all the potential problems with 3D, this is the big one. If your binocular vision isn't perfect, 3D images may appear blurry - and that will soon have you reaching for the Nurofen. But that's as bad as it gets.

As Larry Benjamin puts it: "You cannot damage your eyes by watching a 3D film, but if you spend an excessive period of time doing so, you may get a slight headache because of eyestrain."